Detection of volatile chemicals using an RFID sensing system

ABSTRACT

Methods, systems, and apparatuses, including computer programs encoded on computer-readable media, for monitoring volatile chemicals. A system includes an radio-frequency identification (RFID) tag composed of a patterned metal. The patterned metal is configured to absorb a volatile chemical. The RFID tag includes a non-volatile memory configured to store identification data. The RFID tag also includes a receiver that receives a signal at a frequency in a frequency range. The frequency is based upon an amount of the volatile chemical absorbed in the patterned metal. A transmitter of the RFID tag transmits the identification data in response to receiving the signal. The strength of the transmitted identification data is based upon an amount of the absorbed volatile chemical.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application under 35 U.S.C. § 121 ofU.S. application Ser. No. 14/768,532, filed on Aug. 18, 2015, now U.S.Pat. No. 9,482,639, which is a U.S. National Stage filing under 35U.S.C. § 371 of International Application No. PCT/US2013/030144, filedon Mar. 11, 2013, the entire disclosure of which is hereby incorporatedby reference for all purposes in its entirety.

BACKGROUND

The following description is provided to assist the understanding of thereader. None of the information provided or references cited is admittedto be prior art.

Sulphur compounds and other volatile chemicals can be produced whenfossil fuels, such as oil or coal, are burned. Sulphur compounds are anaturally occurring component of fossil fuels. Metal and other inorganicsulphur containing minerals are mined as a by-product of coal. Given thewide range of uses for fossil fuels, monitoring and/or removing sulphurcompounds and/or volatile chemicals is useful.

SUMMARY

In general, one aspect of the subject matter described in thisspecification can be embodied in a system for monitoring volatilechemicals. This includes a radio-frequency identification (RFID) tagcomposed of a patterned metal. T patterned metal is configured to absorba volatile chemical. The RFID tag includes a non-volatile memoryconfigured to store identification data. The RFID tag also includes areceiver that receives a signal at a frequency in a frequency range. Thefrequency is based upon an amount of the volatile chemical absorbed inthe patterned metal. A transmitter of the RFID tag transmits theidentification data in response to receiving the signal. The strength ofthe transmitted identification data is based upon an amount of theabsorbed volatile chemical.

In one implementation, the system includes an RFID reader thatbroadcasts a request signal over a plurality of frequencies in thefrequency range. A response from the RFID tag is received at aparticular request frequency. The strength of the received response isbased upon the amount of absorbed volatile chemical. A level of thevolatile chemical absorbed in the patterned metal is determined basedupon the strength of the received response and the particular requestfrequency.

In one implementation, one or more of the first plurality of productidentifiers comprises barcode information for a product. In anotherimplementation one or more of the first plurality of product identifierscomprises a description of a product or packaging material informationfor the product.

In another implementation, the system includes a flow tube that isconfigured to convey a fluid. The flow tube includes a metallic sectionconfigured to block the request signal and a non-metallic sectionconfigured to allow passage of the request signal. The RFID tag isattached within the flow tube adjacent to the non-metallic windowportion.

In another implementation, the system includes a flow tube that isconfigured to convey a fluid. The flow tube includes an analysischamber. The RFID tag is mounted within the analysis chamber. A firstvalve connects the flow tube to the analysis chamber and is configuredto allow the fluid to flow from the flow tube into the analysis chamber.A second valve connects the flow tube to the analysis chamber and isconfigured to allow the fluid to flow from the analysis into the flowtube.

In another implementation, a transmitter broadcasts a request signalover a request frequency range. A first response is received from anRFID tag in response to broadcasting the request signal at a firstrequest frequency within the request frequency range. The RFID tag iscomprised of a patterned metal that absorbs a first volatile chemical.The strength of the received first response is based upon an amount ofthe first volatile chemical absorbed by the patterned metal. A level ofthe first volatile chemical absorbed in the patterned metal isdetermined based upon the strength of the received first response andthe first request frequency.

Other implementations include corresponding methods, systems,apparatuses, and computer-readable media configured to perform theactions of the various methods.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the following drawings and thedetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings. Like reference numbersand designations in the various drawings indicate like elements.

FIG. 1 illustrates a volatile chemicals monitoring system in accordancewith an illustrative embodiment.

FIG. 2 illustrates a radio-frequency identification (RFID) tag inaccordance with an illustrative embodiment.

FIG. 3 illustrates a portion of a flow tube with an inline RFID tag inaccordance with an illustrative embodiment.

FIG. 4 illustrates a portion of a flow tube with inline RFID tags inaccordance with an illustrative embodiment.

FIG. 5 illustrates a portion of a tube with an analysis chamber thatincludes an RFID tag in accordance with an illustrative embodiment.

FIG. 6 is a flow diagram of a procedure for determining an absorbedlevel of a volatile chemical in accordance with an illustrativeembodiment.

FIG. 7 is a flow diagram of a procedure for transmitting a signalindicating an absorbed level of a volatile chemical in accordance withan illustrative embodiment.

DETAILED DESCRIPTION

Described herein are illustrative methods and apparatuses relating to aremote monitoring system of one or more volatile chemicals. The remotemonitoring system includes one or more RFID tags that absorb one or morevolatile chemicals. In one implementation, the monitoring of thevolatile chemicals can be continuous. In various implementations, theone or more volatile chemicals that can be monitored include, but arenot limited to, hydrogen sulphide, dimethyl sulphoxide and itshomologues, thiophene and substituted thiophense, sulphur dioxide,thiols, sulphides such as CH₃, C₂H₅, C₃H₇, C₄H₉, or any sulphide ofgeneral formula RSR′, dialkyl selenides, dimethyl selenide and itshomologues, other selenium analogs, etc. R and R′ can represent analkane, alkene, or other carbon-containing group of atoms. The RFID tagscan be made of a substance that absorbs one or more of the volatilechemicals. The RFID tags can be made of gold, silver, platinum,tungsten, rhodium, iridium, ruthenium, osmium, palladium, cadmium, etc.The choice of the material for the RFID tags can be based upon how thatmaterial absorbs a volatile chemical that is to be monitored. Forexample, gold RFID tags can be used to monitor hydrogen sulphide orother organic sulphur compounds. As another non-limiting example,platinum or tungsten RFID tags can be used to monitor sulphur dioxide.An RFID reader can be used to broadcast a signal to one or more RFIDtags at a specific frequency or over a frequency range. An RFID tag thatreceives the RFID reader's signal can respond with data, such asidentification data. The power of the signal transmitted from the RFIDtag to the RFID reader can be reduced based upon the amount of volatilechemical absorbed by the RFID tag. The RFID reader can use the power ofthe received signal to determine how much of the volatile chemical theRFID tag absorbed. In another implementation, the radio frequency of thereceived signal can also be used to determine how much of the volatilechemical the RFID tag absorbed. In yet another implementation, thefrequency at which the RFID tag responds is influenced by the amount ofvolatile chemical absorbed by the RFID tag. In this implementation, theRFID reader can broadcast its signal over a frequency range over aperiod of time. The frequency at which the RFID tag responds can be usedto determine the amount of volatile chemical absorbed by the RFID tag.

FIG. 1 illustrates a volatile chemical monitoring system 100 inaccordance with an illustrative embodiment. The volatile chemicalmonitoring system 100 includes an RFID tag 102. While only a single RFIDtag 102 is illustrated in FIG. 1, multiple RFID tags can be monitored bythe volatile chemical monitoring system 100. The RFID tag 102 can be apassive tag that does not include a battery. The passive tag receivespower from the electromagnetic field generated by receiving a signalfrom an RFID reader 106. The RFID tag 102 can also be an active tag thatincludes a battery that provides power to the RFID tag 102. The RFID tag102 can be placed in the path a fluid flowing through a tube 104. TheRFID reader 106 can broadcast a signal using a transmitter 108 which canbe detected by the RFID tag 102. In response, the RFID tag 102 canrespond 110 with data, such as, but not limited to, an identifier of theRFID tag, a location, an identifier of the tube 104, etc.

FIG. 2 illustrates a radio-frequency identification (RFID) tag 202 inaccordance with an illustrative embodiment. The RFID tag 202 can bedesigned to absorb particular volatile chemicals, such as sulphides 204that have the general formula RSR′. To absorb sulphides 204, the RFIDtag 202 can be composed of a material that is a strong absorbent fororganic sulphur compounds, such as, but not limited to, gold, silver,noble metals, etc. Sulphides 204 can bind with the RFID tag 202 throughat least the sulphur atoms of the sulphide 204.

In other implementations, the RFID tag can be made of a material that isa strong absorbent for sulphur dioxide, such as, but not limited to,platinum, tungsten, etc. Platinum has a strong affinity for sulphur asevidenced by the very low solubility of platinum sulphide and by its useas a catalyst for the oxidation of sulphur dioxide to sulphur trioxidewith air. Tungsten can be used in the RFID tag since tungsten can formnumerous strongly bonded tungsten sulphides. Both platinum and tungstenstrongly chemisorb sulphur dioxide onto their surface. In addition toplatinum and tungsten, other soft polarizable metals can be used in theRFID tag.

Sulphur dioxide can bind to the material of the RFID tag throughsulphur, oxygen, or both atoms. The bonding mode can be predicted basedon the hard and soft acid-base concept. Hard non-polarizable atomspreferentially bind to each other as do soft polarizable atoms. Oxygenis a hard non-polarizable atom and sulfur is a soft polarizable atom.Since sulphur is less prevalent in emission gases than oxygen, an RFIDtag with platinum or tungsten will target binding the sulphur atom insulphur dioxide.

The absorbed volatile chemical occurs at least on portions of the RFIDtag that receives the radio signal from an RFID reader. The portions canbe a patterned metal made by printing and curing a metallic ink. Theremay be advantages in patterning the metal RFID by printing it with ametallic ink followed by sintering. The approach creates an unevenmetallic surface that retains the high resistivity of the metal RFID byleaves a surface with more absorption area and adherence sites for thevolatile chemical. The absorbed volatile chemical can also occur onportions of the RFID tag that transmit a radio signal to the RFIDreader. Accordingly, the intensity and wavelength of the radio signalreceived by the RFID tag, as well as, the radio signal transmitted bythe RFID tag is affected by the amount of the volatile chemical absorbedby the RFID tag.

An RFID tag can be made through various processes. In oneimplementation, an RFID tag can be printed onto a flexible substratesuch as polyimide kapton or polyester mylar. The printing can be doneusing an ink or paste that includes the appropriate material that willabsorb the desired volatile chemical. For example, the ink can includegold, silver, platinum, tungsten, etc. In another implementation,nanoparticles of the selected material can be used to formulate the inkor paste. The RFID tag can be printed on a substrate as a pattern. Theprinted metal pattern can then be thermally cured. The RFID tag is thuscomposed of a patterned metal.

When the RFID tag is printed onto a flexible substrate, the RFID tag isflexible enough to be fitted into various existing components. Forexample, an RFID tag can be inserted into a flow tube that exposes theRFID tag to a flowing fluid, while still allowing the fluid to flowthrough the flow tube. In one implementation, the flow tube can be madeof material that is transparent to radio waves, such as a syntheticpolymer. Existing metal tubes, which can be non-transparent to radiowaves, can also be equipped with RFID tags. For example, the flow tube300 can include metallic portions 302 that are made of metal or othermaterials, which prohibit the passing of radio signals from an RFIDreader. Accordingly, the RFID tag 306 can be placed in a non-metallicportion 304, that allows the RFID tag to be interrogated from outside ofthe flow tube 300. The non-metallic portion 304 can be made of adielectric or a synthetic polymer. In one implementation, the RFID tagcan be placed at the top of the flow tube without requiring anon-metallic portion. In other implementations, the RFID tag can beplaced in the interior of the flow tube if a synthetic polymer portionis inserted into the metal flow tube. FIG. 3 illustrates a portion of aflow tube 300 with an inline RFID tag 306 in accordance with anillustrative embodiment. The flow tube 300 can be a flue for exhaust.For example, the flow tube 300 can move flue gases from power plants,home heating units, gas pipelines, or tailpipes of vehicles. As anon-limiting example, the flow tube can be a flow tube for emissionsfrom burning natural gas.

FIG. 4 illustrates a portion of a flow tube 400 with inline RFID tags406 in accordance with another illustrative embodiment. In thisillustrated example, RFID tags 406 can be made to fit the inner diameterof the flow tube 400. The RFID tags 406 are, therefore, exposed to a gasas the gas moves through the flow tube 400. Similar to FIG. 3, the RFIDtags 406 are located in a non-metallic portion 404, that allows the RFIDtag to be interrogated from outside of the flow tube 400. The flow tube400 can also include metallic portions 402, which can inhibit the RFIDreader's transmissions.

In another implementation, an analysis chamber can be used. In thisimplementation, an RFID tag can be used in a metal flow tube that doesnot require major modification to the integrity of the metal flow tube.FIG. 5 illustrates a portion of a flow tube 502 with an analysis chamber510 that includes an RFID tag 508 in accordance with an illustrativeembodiment. The RFID tag 508 can be placed in parallel with the flowinggas in the flow tube 502 inside the analysis chamber 510. The RFID tag508, however, is not included inline within the flow tube 502. In thisimplementation, the flow tube 502 can be comprised of a metal and theanalysis chamber 510 can be made of a material that is transparent toradio waves. The analysis chamber 510 is connected to the flow tube 502through two valves 504 and 506. The valves 504 and 506 can be openedwhen an analytical sample is needed. The opening and closing of thevalves 504 and 506 can be timed to correspond with the reading of theRFID tag 508 or the usage of the flow tube 502. For example, the valves504 and 506 can be opened when there is a fluid flowing through the flowtube 502. In another implementation, the valves 504 and 506 can beopened some amount of time, e.g., 5 minutes, 30 minutes, 60 minutes,prior to the reading of the RFID tag 508. In yet another implementation,the valves 504 and 506 can be opened on a predetermined schedule. Thevalves 504 and 506 can also be controlled by the RFID tag. For example,the RFID tag can control the opening and closing of the valves 504 and506 based upon receiving signals from an RFID reader. For example, theRFID tag can open the valves 504 and 506 when a first signal isreceived. When the RFID tag receives another signal, the valves 504 and506 can be closed. In one example, the RFID tag can include a batterythat provides power to components that open and close the valves 504 and506. A gas flushing loop can be incorporated into the opening andclosing of the valves 504 and 506 to flush the analyte gases out of theanalysis chamber 510. For example, the opening and closing of the valves504 and 506 can be sequenced, such that the valves 504 and 506 areopened, the RFID tag 508 is read, and then the analyte gases can beflushed from the analysis chamber 510.

The RFID tags described above can be used to continually monitorvolatile chemicals in a flowing gas. As the monitored volatile chemicalis absorbed into the RFID tag, the characteristics of the RFID tagchange. For example, the frequency at which an RFID tag responds canchange based upon the amount of volatile chemical absorbed by the RFIDtag. An RFID reader can broadcast a signal over a frequency range anddetermine at which frequency the RFID tag responds. If differentvolatile chemicals have their maximum radio-frequency absorption indifferent wavelength ranges, an RFID reader can selectively detect eachof the volatile chemicals by using read frequency ranges specific to thewavelength ranges of the volatile chemicals. Empirical data can be usedto map a response frequency to an amount of volatile chemical absorbed.For example, a clean RFID tag can be used to determine a base frequencythat signifies that the RFID tag has not absorbed a detectable amount ofthe volatile chemical. RFID tags can then be coated with volatilechemicals that are to be monitored. The response radio frequency of eachcoated RFID tag can then be determined by an RFID reader broadcastingover a frequency range and noting when a particular RFID tag responds.The amount of volatile chemical absorbed by the RFID tag can also impactthe strength of the signal transmitted by the RFID tag. The impact onthe strength of the signal based upon the amount of volatile chemicalabsorbed can also be determined empirically. The amount of volatilechemical absorbed by the RFID tag can also impact the strength of thesignal received by the RFID tag. The impact on the strength of thesignal based upon the amount of volatile chemical absorbed can also bedetermined empirically. An RFID reader can broadcast a signal over apower range. For example, the RFID reader can start broadcasting thesignal with increasing power. The power at which the RFID tag respondscan be used to determine the amount of volatile chemical absorbed by theRFID tag. Alternatively, the RFID reader can broadcast the signal over adecreasing power range. The last power at which the RFID tag respondscan be used to determine the amount of volatile chemical absorbed by theRFID tag. Background readings can be taken to confirm if there areinterferences from hydrocarbons or other components that are not desiredto be monitored.

A monitoring system can be constructed using one or more RFID tags andat least one RFID reader. The RFID tags can be placed in variouslocations, such as in or near flow tubes. As gases pass over the RFIDtags, the RFID tags absorb one or more volatile chemicals. The volatilechemical absorbed is based upon the material of the RFID tag. The RFIDreader can then broadcast a radio signal to the RFID tags. Responsesfrom the RFID tags can be used to determine how much of the respectivevolatile chemical each RFID tag has absorbed.

FIG. 6 is a flow diagram of a procedure 600 for determining an absorbedlevel of a volatile chemical in accordance with an illustrativeembodiment. Additional, fewer, or different operations of the procedure600 may be performed, depending on the particular embodiment. Theprocedure 600 can be implemented on a computing device. In oneimplementation, the procedure 600 is encoded on a computer-readablemedium that contains instructions that, when executed by a computingdevice, cause the computing device to perform operations of theprocedure 600.

An RFID reader can broadcast a request signal over a frequency range toone or more RFID tags (610). For example, an RFID reader that ismonitoring a particular volatile chemical, such as hydrogen sulphide,can broadcast the request signal over a frequency range associated withhydrogen sulphide. The frequency range associated with hydrogen sulphidecan be determined empirically, as described in greater detail above. Thefrequency range is wide enough to cover when the RFID tag has notabsorbed any of the volatile chemical and when the RFID tag has absorbeda maximum amount of the volatile chemical. The RFID reader receives aresponse from an RFID tag at a frequency (620). The response can includeinformation that can identify the particular RFID tag or a location ofthe RFID tag. The strength of the received signal as well as thereceived frequency can be used to determine the amount of volatilechemical that the RFID tag has absorbed (630). In other implementations,using only the received frequency or received signal strength can beused to determine the amount of volatile chemical that the RFID tag hasabsorbed. Determining the amount of volatile chemical absorbed by theRFID tag can be used to monitor changes in concentration of the volatilechemical in the gas that flows over the RFID tag.

FIG. 7 is a flow diagram of a procedure 700 for transmitting a signalindicating an absorbed level of a volatile chemical in accordance withan illustrative embodiment. Additional, fewer, or different operationsof the procedure 700 may be performed, depending on the particularembodiment. Once placed in its desired location, a patterned metal of anRFID tag absorbs a volatile chemical (710). The RFID tag receives asignal at the response frequency of the RFID tag (720). For example, thereceived signal can be from an RFID reader. The response frequency ofthe RFID tag is dependent on the amount of volatile chemical absorbed bythe RFID tag. Accordingly, the response frequency for an RFID tag willchange as the RFID tag absorbs more of the volatile chemical. Based uponreceiving the signal at the response frequency, the RFID tag transmitsidentification data (730). In one implementation, the RFID tag transmitsat a constant power. The absorbed volatile chemical, however, can absorba portion of the transmitted signal, thereby, lowering its power. TheRFID tag can power its transmitter using a battery or through the energyprovided by receiving the signal at the response frequency. As describedin greater detail above, the RFID reader can determine the amount ofvolatile chemical absorbed by the RFID tag based upon the frequency atwhich the RFID tag responded and/or by the strength of the signalreceived by the RFID reader.

EXAMPLES

The present systems and methods will be understood more readily byreference to the following example, which is provided by way ofillustration and is not intended to be limiting in any way.

Example 1: Methanethiol Example

An RFID tag can be configured to absorbed methanethiol. As the RFID tagabsorbs methanethiol, the intensity of a signal received by the RFID tagand also the intensity of a signal transmitted from the RFID tag willchange based upon one or more factors. For example, the absorption ofthe organic sulfur compound at the chosen microwave frequency, whichwill depend on the molar absorptivity ∈ of the organic sulfur compoundat that frequency, can affect the intensity of signals. A second factoris the thickness of the adsorbed layers of the organic sulfur compoundon the surface of the RFID tag. The absorption of the microwaveradiation (electromagnetic radiation) is expected to follow theBeer-Lambert (Beer's) Law, namely A=∈cl where, for the organic sulfurcompound, A is the absorbance, ∈ is the molar absorptivity inl·mol⁻¹·cm⁻¹, c is the concentration in moles per liter, and l is thepath length (thickness) expressed in cm. Molar absorptivities ∈ canrange from 5 to 2,000.

Taking methanethiol (CH₃SH) with a molecular weight of 48 as an example;pure methanethiol that has a density of approximately 0.9 g·cm⁻³absorbed onto the surface of an RFID will have a concentration c of18.75 moles liter⁻¹. Assuming a molar absorptivity ∈ of 5×10²l·mol⁻¹·cm⁻¹ and a layer thickness of methanethiol on the RFID surfaceof 100 molecules, the path length l will be approximately 2×5×10⁻⁶ cm ifa single molecular layer of methanethiol has a thickness of 500picometers (pm). The factor of 2 results from the incident radiationbeam passing through a 500 picometer thickness of methanethiol as ittransmits through the methanethiol layer for passage both to and fromthe surface of the RFID tag. Applying Beer's Law gives:A=(5×10²)×18.75×(10×10⁻⁶)=93.75×10⁻³ or 0.09375

The absorbance A is defined by equation A=−log I/I_(o) where I is thetransmitted intensity after passage through the methanethiol layer andI_(o) is the incident (initial) intensity, or the intensity from a cleanRFID tag. The ratio I/I_(o) is therefore the transmittance.

In one implementation, the system is designed for the absorbance A to bewithin the range of >0 to 2, because the transmittance needs to bewithin a measureable range. If the transmittance is too high theintensity of the radiation I will be within statistical error of theinitial I_(o) value, whereas if the transmittance is too low theintensity of the radiation I will be too low to get a measureable valueabove the baseline value of the instrument. The following examples showthese trends:

For A=4×10⁻³, 0.3 and 2, the transmittance I/I_(o) is 0.99 (99%),0.5(50%) and 0.01 (1%), respectively.

Implementations of portions of the subject matter and the operationsdescribed in this specification can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them. The subjectmatter described in this specification can be implemented as one or morecomputer programs, i.e., one or more modules of computer programinstructions, encoded on one or more computer storage media forexecution by, or to control the operation of, data processing apparatus.Alternatively or in addition, the program instructions can be encoded onan artificially-generated propagated signal, e.g., a machine-generatedelectrical, optical, or electromagnetic signal that is generated toencode information for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal, a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially-generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate components or media (e.g., multiple CDs, disks, or otherstorage devices). Accordingly, the computer storage medium is bothtangible and non-transitory.

The term “data processing apparatus” or “computing device” encompassesall kinds of apparatus, devices, and machines for processing data,including by way of example a programmable processor, a computer, asystem on a chip, or multiple ones, or combinations of the foregoing.The apparatus can include special purpose logic circuitry, e.g., an FPGA(field programmable gate array) or an ASIC (application-specificintegrated circuit). The apparatus can also include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, across-platform runtime environment, a virtual machine, or a combinationof one or more of them. The apparatus and execution environment canrealize various different computing model infrastructures, such as webservices, distributed computing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto-optical disks, or optical disks.However, a computer need not have such devices. Moreover, a computer canbe embedded in another device, e.g., a mobile telephone, a personaldigital assistant (PDA), a mobile audio or video player, a game console,a Global Positioning System (GPS) receiver, or a portable storage device(e.g., a universal serial bus (USB) flash drive), to name just a few.Devices suitable for storing computer program instructions and datainclude all forms of non-volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features described in this specification in thecontext of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresdescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated in a single software product or packagedinto multiple software products.

One or more flow diagrams have been used herein. The use of flowdiagrams is not meant to be limiting with respect to the order ofoperations performed. The herein-described subject matter sometimesillustrates different components contained within, or connected with,different other components. It is to be understood that such depictedarchitectures are merely exemplary, and that in fact many otherarchitectures can be implemented which achieve the same functionality.In a conceptual sense, any arrangement of components to achieve the samefunctionality is effectively “associated” such that the desiredfunctionality is achieved. Hence, any two components herein combined toachieve a particular functionality can be seen as “associated with” eachother such that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected” or “operablycoupled” to each other to achieve the desired functionality, and any twocomponents capable of being so associated can also be viewed as being“operably couplable” to each other to achieve the desired functionality.Specific examples of “operably couplable” include but are not limited tophysically mateable and/or physically interacting components and/orwirelessly interactable and/or wirelessly interacting components and/orlogically interacting and/or logically interactable components.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

The foregoing description of illustrative embodiments has been presentedfor purposes of illustration and of description. It is not intended tobe exhaustive or limiting with respect to the precise form disclosed,and modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the disclosed embodiments.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

What is claimed is:
 1. A non-transitory computer-readable medium havingstored thereon computer-executable instructions that, in response toexecution by one or more processors, cause the one or more processors toperform or control performance of operations to: broadcast a requestsignal over a request frequency range; obtain a first response from aradio-frequency identification (RFID) tag, in response to the broadcastof the request signal at a first request frequency within the requestfrequency range, wherein the RFID tag is composed of a patterned metal,and wherein the patterned metal absorbs a first volatile chemical; senda first command to the RFID tag at the first request frequency to open afirst valve, wherein the first valve allows a fluid to flow over theRFID tag; send a second command to the RFID tag at the first requestfrequency to close the first valve; and determine a level of the firstvolatile chemical absorbed in the patterned metal based upon the firstrequest frequency.
 2. The non-transitory computer-readable medium ofclaim 1, wherein the computer-executable instructions that, in responseto execution, further cause the one or more processors to perform atleast one operation to: obtain a second response from the RFID tag, inresponse to the broadcast of the request signal at a second requestfrequency within the request frequency range, wherein the patternedmetal absorbs a second volatile chemical; and determine a level of thesecond volatile chemical absorbed in the patterned metal based upon thesecond request frequency.
 3. The non-transitory computer-readable mediumof claim 1, wherein the patterned metal absorbs the first volatilechemical from the fluid.
 4. The non-transitory computer-readable mediumof claim 1, wherein the patterned metal comprises gold or silver.
 5. Thenon-transitory computer-readable medium of claim 4, wherein the firstvolatile chemical absorbed by the patterned metal comprises one of asulfide and a thiol.
 6. The non-transitory computer-readable medium ofclaim 1, wherein the patterned metal comprises platinum or tungsten. 7.The non-transitory computer-readable medium of claim 6, wherein thefirst volatile chemical absorbed by the patterned metal comprisessulphur dioxide.
 8. A sensor to detect a volatile chemical, the sensorcomprising: a chamber that comprises a polymer section, wherein thechamber is configured to allow a flow of a fluid, and wherein thechamber is connected to the polymer section through one or more valves;a substrate attached onto an inner wall of the polymer section of thechamber; and a radio-frequency identification (RFID) tag formed on asurface of the substrate, wherein the RFID tag is communicativelycoupled to an RFID reader, and wherein the RFID tag is composed of apatterned metal configured to absorb the volatile chemical, the RFID tagcomprising: a non-volatile memory having stored thereon computerexecutable instructions that, in response to execution by one or moreprocessors, cause the one or more processors to perform or controlperformance of operations to: obtain a request signal at a frequency ina frequency range, wherein the frequency is based upon an amount of thevolatile chemical absorbed in the patterned metal, wherein a firstsignal is obtained from the RFID reader to open the one or more valves,and wherein a second signal is obtained from the RFID reader to closethe one or more valves; and transmit identification data in response tothe obtained request signal, wherein a strength of the transmittedidentification data is based upon the amount of the volatile chemicalabsorbed in the patterned metal.
 9. The sensor of claim 8, wherein thepatterned metal is configured to absorb the volatile chemical from thefluid.
 10. The sensor of claim 8, wherein a strength of the requestsignal is based upon the amount of the volatile chemical absorbed in thepatterned metal.
 11. The sensor of claim 8, wherein the RFID reader isconfigured to: broadcast the request signal over a plurality offrequencies in a request frequency range; receive a response from theRFID tag at a particular request frequency; and determine a level of thevolatile chemical absorbed in the patterned metal based upon a strengthof the received response from the RFID tag and the particular requestfrequency.
 12. The sensor of claim 8, wherein the polymer sectioncomprises polytetraflouroethylene.
 13. The sensor of claim 8, whereinthe substrate comprises one of a polyimide film and a biaxially-orientedpolyethylene terephthalate.
 14. The sensor of claim 8, wherein thepatterned metal comprises gold or silver.
 15. The sensor of claim 14,wherein the volatile chemical absorbed by the patterned metal comprisesone of a sulfide or a thiol.
 16. The sensor of claim 8, wherein thepatterned metal comprises platinum or tungsten.
 17. The sensor of claim16, wherein the volatile chemical absorbed by the patterned metalcomprises sulphur dioxide.